- Trading: It is called a way to get more money by trading cryptos, either by transferring between them or by providing exchange services.
- Investment: There are many cryptocurrencies with a good future, but I only recommend Bitcoin and Ethereum.
- Gambling: sometimes beneficial and sometimes detrimental. I don't recommend it at all (risk high)
Don't invest yet until you're able to understand the whole concept of cryptocurrencies and how volatile this market is.
Gambling should not be there as it is not a sector where cryptocurrencies are being used but it is an application which is prominently making use of cryptocurrencies which might be the reason why you are considering it along with trading and investments.